The present invention relates to a cooling system in a motor vehicle.
Conventional cooling systems for cooling a combustion engine in a motor vehicle usually comprise a radiator situated in a front portion of the vehicle. Such a radiator location results in a natural cooling air flow through the radiator, but a radiator fan is usually applied to the radiator to ensure that a required air flow is maintained through the radiator during various operating conditions. However, the space in the front portion is limited. Like other spaces in the vehicle, it is also subject to competition from other components of the vehicle. This means that the radiator cannot be larger than a certain size. The capacity of conventional cooling systems is limited by the amount of space available for the radiator in the front portion of the vehicle.
However, the cooling requirements of heavy vehicles are constantly increasing, partly because ever more powerful engines are being used. Another reason is the ever more stringent requirements concerning discharges of exhaust gases, particularly from diesel engines. To provide diesel engines which meet the ever more stringent requirements, it is possible for part of their exhaust gases to be recirculated (EGR, exhaust gas recirculation). Such recirculation reduces discharges of nitrogen oxides, but this method requires cooling of the recirculating exhaust gases. There is also ever increasing use of supercharged combustion engines with ever higher pressures. Vehicle fuel consumption can thereby be reduced, but cooling of the compressed air is required before it is led to the diesel engine. To this end, a so-called charge air cooler is usually employed close to the vehicle's ordinary radiator at the front of the vehicle.
Conventional cooling systems provided only with a radiator at the front of the vehicle are likely to have difficulty in meeting the total cooling requirements of future vehicles, particularly in situations where the vehicle is operated in a hot environment and/or the combustion engine is subject to long periods of high load.
A known practice is to use a cooling system equipped with more than one radiator. A difficulty in such cases is finding a suitable space in the vehicle for fitting such an extra radiator. Such a space needs to be large enough to be able to accommodate a radiator while at the same time being situated in the vehicle in such a way as to make it easy for an air flow to be led through the radiator.